I think the fundamental problem is keeping the huge bio tanks hermetically clean. The cleaning process is very energy intensive as is the medium growing process

I think the fundamental problem is keeping the huge bio tanks hermetically clean. The cleaning process is very energy intensive as is the medium growing process. One way to cut cost would be to introduce small cells that seek out and destroy pathogens. We could design a bio tank organ that creates these cells by eating some of the growth medium. Also instead of using a medicine grade medium we could use organic sacks that grow bacteria from plant matter. Then we could move said bacteria to sacks filled with acid that would extract energy to create more biomatter. Some of the excess energy could be used for the bio-tank to locomote around in the environment and harvest plant matter for digestion. Also by using genetic code we could make these new and improved bio tanks self-replicate. We could call these new devices Clean Organic Walkers, or Cows for short.